1. Field of the Invention
The present invention relates to a device for opening and closing an original pressing device which presses an original to an original supporting table of a copier, printer or the like.
2. Description of the Prior Art
Generally, the original pressing devices of this type include ones provided with an automatic original feeding apparatus and ones not provided with such an apparatus. In the former type of original pressing device, an original is automatically fed to an original supporting table by an original conveying belt and automatically evacuated from the original supporting table by the original conveying belt after a copying is made. For manually setting an original in place on the original supporting table or removing the original from on the original supporting table, the original pressing device is installed to the body of a copier for example with an opening-closing device provided between the original pressing device and copier body to facilitate opening or closing of the original pressing device. Normally, a pair of such opening-closing devices is used. For manual operation of the original pressing, the opening-closing device is constructed as follows for easy opening, to a desired intermediate angular position, of the original pressing device provided with an automatic original feeding apparatus which is sufficiently heavy to set and hold an original in place on the original supporting table, and holding the original pressing device stably at the angular position with no likelihood that the original pressing device will spontaneously fall onto the original supporting table even with the hand taken off the original pressing device. That is, the opening-closing device includes a base member for fixation to the body of a copier for example, a supporting member secured pivotably to the base member with a hinge pin and on which the original pressing device is fixed at the rear portion thereof, and an elastic member provided between the base and supporting members to elastically force the supporting member in the opening direction.
Normally, the above opening-closing devices, right and left, are provided in pair on the body of the copier and the elastic members will lift somehow the original pressing device at the opening-closing devices when the original pressing device is opened. For these reasons, there takes place a problem that the original conveying belt of the original pressing device cannot be pressed horizontally to the original supporting table, an original to be fed is moved obliquely and thus cannot be set in place, or the original cannot correctly be evacuated from on the original supporting table after a copying is made. The original pressing device cannot be set horizontally on the original supporting table when it does not dimensionally fit to the table or when the user of the copier replaces the regular original pressing device with a one with an automatic original feeding apparatus. To avoid the above, the following opening-closing device for an original pressing device has been proposed (as in the Japanese Unexamined Patent Publication No. 9-208098), which includes a base member to be fixed vertically slidably to the body of a copier for example by means of a supporting foot, a supporting member for an original pressing plate, secured at one end thereof pivotably to the base member with a hinge pin, and an elastic member provided between the free end of the supporting member and the base member to elastically force the supporting member in the direction in which the original pressing device can be opened, the opening-closing device further including a fixing plate provided between the supporting member and original pressing plate and on which a roller is installed.
This conventional opening-closing device is adapted to automatically position the original pressing device horizontally in relation to the original supporting table. Therefore, no fine adjustment is required after installation of the original pressing device and opening-closing device. However, a roller for smooth sliding of the hinge foot, roller provided on the original pressing device, etc. have to additionally be provided, so that the original pressing device with the opening-closing device has a complicated structure which will lead to an increased manufacturing cost.